Download Altec Lansing 1270 User's Manual
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ALTEC POWER E Mia ==) INTRODUCTION The ALTEC LANSING Model 1270 Power Amplifier provides continuous high power demand where uninterrupted operation is requisite. Designed to protect itself and the acoustic elements it drives, the Model 1270 represents 800 + watts of controlled power. Two channels may be operated independ- ently, in parallel or in bridged configuration to deliver up to 400 watts per channel at less than 0.05% THD from 20 Hz to 20 kHz. Peak Error Computer The amplifier is provided with a peak/error computer that compares channel input and output signals and detects any output errors. Detection of any peak/error causes the appropriate peak/error indicator to illu- minate. Output anomalies detected include excessive voltage, excessive current (load), excessive slew rate, and any other signifi- cant difference between the channel input and output signal. Amplifier Protection The amplifier output is continuously mon- itored to guard against excessive current drain. An instantaneous VI limiter restricts output to 400 VA +45* phase shift. The amplifier is additionally protected against excessive operating temperature; logic cir- cuitry automatically overrides low-speed fan operation and locks to the high fan speed mode. If operating temperature remains excessive, the load is discon- nected by a relay and the protection indica- tor illuminates. When temperature falls to safe operating conditions, the amplifier automatically resumes operation. LANSING | ALTEC LANSING’ 1270 POWER AMPLIFIER OPERATING INSTRUCTIONS CAUTION: IMPORTANT: qualifié. No user-serviceable parts inside. Hazardous voltage may be en- countered within the chassis. Installation and Service information within this document is for use only by ALTEC sound contractors, factory authorized warranty stations and qualified service personnel. Il est enjoint à l'utilisateur de ne pas réparer lui-même les pièces internes de l'appareil, des courants à haute tension pouvant pas- ser à l'intérieur du châssis. Les renseignements inclus dans ce document sont destinés uniquement à l'usage des installateurs agréés des systèmes acoustiques ALTEC, des centres de réparation sous garantie autorisés, ainsi que du personnel d'entretien Load Protection The load is protected from transients dur- ing startup and shutdown of the amplifier. During startup, the load remains discon- nected through a relay during a three- FRONT PANEL CONTROLS AND FEATURES second delay period. During shutdown or loss of power, the load is instantaneously disconnected by the relay. The load is simi- larly protected against amplifier failure, such as dc voltage at the output. Item Name Function/Description 1 Peak/Error Indicators 2 Protection Indicator 3 |POWER Indicator 4 | POWER Switch 5 | CHANNEL Volume Controls increase gain. Illuminate when excessive voltage, current or slew rate ap- pears at the output terminals. Illuminates when protection circuitry operates to prevent dam- age to the amplifier or load. Illuminated when primary ac power is applied to the amplifier. Applies primary ac power to the amplifier. Adjust gain of LEFT and RIGHT channels. Rotate clockwise to 1515 S. Manchester Ave., Anaheim, Calif. 92803 Specifications and components subject to change without notice. Overall performance will be maintained or improved. 42-02-045589-01 LITHO IN U.S.A. 681-1M INSTALLATION Rack Mounting The 1270 may be installed in a standard 19-inch equipment rack, or in the 42526 Shelf Mount Cover Accessory for shelf use. Vertical space required is 51”. Rack instal- lation is accomplished by using the appro- priate four mounting screws supplied. Ventilation The 1270 must be adequately ventilated to prevent excessive temperature rise. Max- imum rated ambient operating temperature is 55°C (131°F). CAUTION Do not block the side ventilation aperatures on either side of the main frame. Allow at least 2” on each side of the main frame to assure adequate ventilation. Do not operate within a completely closed, unventilated housing. REAR PANEL CONTROLS AND FEATURES ELECTRICAL 120 Volt, 50/60 Hz Power Connections Equipment supplied for domestic use is provided with the power transformer primary strapped for 120 volts. Specified voltage rating is located on the chassis, adjacent to the power cord. Verify that line voltage is in accordance with specified volt- age before connecting the 1270 to ac line power. 100V, 200V, 220V, 240V, 50/60 Hz Power Connections Refer to Authorized Altec Service Representative. Input Connections Unbalanced input connections to the INPUT jacks are made with shielded single- conductor cables terminated with standard '4-inch phone jacks. In preparing the cable, the conductor is soldered to the tip of the jack, and the shield is soldered to the sleeve. fa A hd ET = LTE 23] MADE 7 EA Item Name Function/Description 1 OUTPUT Terminals 2 {INPUT Receptacies (r) receptacles. 3 ILINE Receptacles receptacles. 4 |BRIDGE/ NORMAL Switch into 8 ohms. 5 | COM Terminal 6 |GND Terminal 7 | FAN Switch 8 Fuse Connect left (L) and right (R) channels to corresponding speak- ers. Two pair of standard GR jacks have red (+) and black (—) polarity designations. Accept cables from high impedance (nominal 15,000 ohms) sources. Use standard ring and sleeve plug for left (L) and right Accept cables to connect other Altec Amplifiers in parallel. Use standard ring and sleeve plug for left (L) and right (R) Connects internal circuitry for independent or mono operation (NORMAL) into a 4-ohm load, of bridge operation (BRIDGE) Provides connection to circuit common. Provides connection to chassis ground. Selects low (1) or high (2) fan speed. Protects amplifier from excessive current drain. Replace only with same type 10-ampere fuse, Refer to qualified service per- sonnel if fuse blows repeatedly. Balanced input connections are made with the optional 1270TM Dual Balanced Trans- former Input Module. Plug the 1270TM into the INPUT receptacles of the 1270 and secure the retaining screw. See Figure 1. Cables terminated with XLR3-type connec- tors are used to make input connections to the 1270 TM module; wiring for the XLR3- type connector is shown in Figure 2. SECURING SCREW TRANSFORMER MODULE INPUT RECEPTACLES MODULE JACKS CHANNEL INPUT RECEPTACLES 1b. Module Installed Figure 1. Installation of 1270TM Module WHT i, mT XLR3 PLUG Figure 2. Wiring for XLR3-type Connector Line Qut Connections Connections to LINE OUT receptacles are made with shielded single-conductor cables terminated with standard '-inch phone jacks. When channels are operated independently (stereo operation) a cable must connect each channel of each addi- tional 1270 amplifier connected in multiple. When channels are operated in the bridge mode, only the left channel of each addi- tional 1270 requires a connecting cable. Output Connections Output connections are made at the L and R OUTPUT terminals. Figure 3 illustrates connections for independent (stereo) opera- tion and for bridged operation. GND and COM Connections The GND (chassis ground) and COM (elec- trical common) terminals are used to cor- rect unsatisfactory grounding conditions and for establishing desired grounding configurations. cu 3a. Independent Operation of L and R Channels OUTPUT HE NOT CONNECTED Te 80 NOT CONNECTED CAUTION —— Bridged operaton provides a true bal- anced output. Do not connect either side of the loudspeaker line to audio common or to any other “ground” connection. 3b. Bridge Operation of L and R Channels Figure 3. Output Connections STEREO (INDEPENDENT CHANNEL) OPERATION 1. > After installation and hookup of connec- tions as in Figure 3A, check that the BRIDGE/NORMAL switch is positioned at NORMAL, and that the LEFT and RIGHT CHANNEL volume controls are turned fully counterclockwise. («). Set input signal level to the 1270 at a nominal value of 0.775V. Turn on ac line POWER switch and note illumination of POWER indicator. Turn LEFT and RIGHT CHANNEL vol- ume controls clockwise until desired output power is obtained. If either LEFT or RIGHT peak/error indicator illumi- nates, reduce output level with channel volume control or reduce input level to 1270. BRIDGE (MONO) OPERATION 1. After installation and hookup of connec- tions as in Figure 3B, check that the BRIDGE/NORMAL switch is positioned at BRIDGE, and that the LEFT and RIGHT CHANNEL volume controls are turned fully counterclockwise (co). Set input signal level to the left (L) INPUT of the 1270 at a nominal value of 0.775V. (The right (R) INPUT is left unconnected.) 3. 4. Turn on ac line POWER switch and note illumination of POWER indicator. Turn LEFT CHANNEL volume control clockwise until desired output power is obtained. Be sure to leave RIGHT CHAN- NEL volume control fully counterclock- wise. If LEFT peak/error indicator illu- minates, reduce output level with LEFT CHANNEL volume control, or reduce input level to the 1270.
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